rpc_client.hpp

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#pragma once
 
#include <nui/frontend/val.hpp>
 
#include <traits/functions.hpp>
#include <nui/frontend/api/console.hpp>
#include <nui/frontend/utility/functions.hpp>
#include <nui/frontend/utility/val_conversion.hpp>
#include <nui/shared/on_destroy.hpp>
 
#include <string>
#include <cstdint>
#include <tuple>
 
namespace Nui
{
    namespace Detail
    {
        template <typename ReturnType, typename ArgsTypes, typename IndexSeq>
        struct FunctionWrapperImpl
        {};
 
        template <typename ArgT>
        constexpr static auto extractMember(Nui::val const& val) -> decltype(auto)
        {
            if constexpr (std::is_same_v<std::decay_t<ArgT>, Nui::val>)
                return val;
            else
            {
                std::decay_t<ArgT> value;
                convertFromVal(val, value);
                return value;
            }
        }
 
        template <typename ReturnType>
        struct FunctionWrapperImpl<ReturnType, std::tuple<Nui::val>, std::index_sequence<0>>
        {
            template <typename FunctionT>
            constexpr static auto wrapFunction(FunctionT&& func)
            {
                return [func = std::forward<FunctionT>(func)](Nui::val const& args) mutable {
                    func(args);
                };
            }
        };
 
        template <typename ReturnType, typename ArgType>
        struct FunctionWrapperImpl<ReturnType, std::tuple<ArgType>, std::index_sequence<0>>
        {
            template <typename FunctionT>
            constexpr static auto wrapFunction(FunctionT&& func)
            {
                return [func = std::forward<FunctionT>(func)](Nui::val const& arg) mutable {
                    func(extractMember<ArgType>(arg));
                };
            }
        };
 
        template <typename ReturnType, typename... ArgsTypes, std::size_t... Is>
        struct FunctionWrapperImpl<ReturnType, std::tuple<ArgsTypes...>, std::index_sequence<Is...>>
        {
            template <typename FunctionT>
            constexpr static auto wrapFunction(FunctionT&& func)
            {
                return [func = std::forward<FunctionT>(func)](Nui::val const& args) mutable {
                    func(extractMember<ArgsTypes>(args[Is])...);
                };
            }
        };
 
        template <typename ReturnType, typename ArgsTypes>
        struct FunctionWrapperImpl2
        {};
 
        template <typename ReturnType, typename... ArgsTypes>
        struct FunctionWrapperImpl2<ReturnType, std::tuple<ArgsTypes...>>
            : public FunctionWrapperImpl<ReturnType, std::tuple<ArgsTypes...>, std::index_sequence_for<ArgsTypes...>>
        {};
 
        template <typename FunctionT>
        struct FunctionWrapper
            : public FunctionWrapperImpl2<
                  typename Traits::FunctionTraits<std::decay_t<FunctionT>>::ReturnType,
                  typename Traits::FunctionTraits<std::decay_t<FunctionT>>::ArgsTuple>
        {};
    }
 
    class RpcClient
    {
      public:
        class RemoteCallable
        {
          public:
            template <typename... Args>
            auto operator()(Args&&... args) const
            {
                using namespace std::string_literals;
                if (!resolve())
                {
                    WebApi::Console::error("Remote callable with name '"s + name_ + "' is undefined");
                    return Nui::val::undefined();
                }
                if (backChannel_.empty())
                    return callable_(convertToVal(args)...);
                return callable_(convertToVal(backChannel_), convertToVal(args)...);
            }
            auto operator()(Nui::val val) const
            {
                using namespace std::string_literals;
                if (!resolve())
                {
                    WebApi::Console::error("Remote callable with name '"s + name_ + "' is undefined");
                    return Nui::val::undefined();
                }
                if (backChannel_.empty())
                    return callable_(val);
                return callable_(convertToVal(backChannel_), val);
            }
 
            bool isValid() const
            {
                return resolve();
            }
 
            explicit operator bool() const
            {
                return isValid();
            }
 
            explicit RemoteCallable(std::string name)
                : name_{std::move(name)}
                , backChannel_{}
                , callable_{Nui::val::undefined()}
                , isSet_{false}
            {}
 
            RemoteCallable(std::string name, std::string backChannel)
                : name_{std::move(name)}
                , backChannel_{std::move(backChannel)}
                , callable_{Nui::val::undefined()}
                , isSet_{false}
            {}
 
          private:
            bool resolve() const
            {
                using namespace std::string_literals;
                if (isSet_)
                    return true;
 
                const auto rpcObject = Nui::val::global("nui_rpc");
                if (rpcObject.isUndefined())
                    return false;
 
                callable_ = Nui::val::global("nui_rpc")["backend"][name_.c_str()];
                isSet_ = !callable_.isUndefined();
                return isSet_;
            }
 
          private:
            std::string name_;
            std::string backChannel_;
            mutable Nui::val callable_;
            mutable bool isSet_;
        };
 
        static auto getRemoteCallable(std::string name)
        {
            return RemoteCallable{std::move(name)};
        }
 
        template <typename... ArgsT>
        static auto call(std::string name, ArgsT&&... args)
        {
            return getRemoteCallable(std::move(name))(std::forward<ArgsT>(args)...);
        }
 
        template <typename FunctionT, typename... ArgsT>
        static auto callWithBackChannel(std::string name, FunctionT&& cb, ArgsT&&... args)
        {
            return getRemoteCallableWithBackChannel(std::move(name), std::forward<FunctionT>(cb))(
                std::forward<ArgsT>(args)...);
        }
 
        template <typename FunctionT>
        static auto getRemoteCallableWithBackChannel(std::string name, FunctionT&& func)
        {
            return RemoteCallable{std::move(name), registerFunctionOnce(std::forward<FunctionT>(func))};
        }
 
        template <typename FunctionT>
        static std::string registerFunctionOnce(FunctionT&& func)
        {
            using namespace std::string_literals;
            if (Nui::val::global("nui_rpc").isUndefined())
            {
                WebApi::Console::error("rpc was not setup by backend"s);
                return {};
            }
            auto tempId = Nui::val::global("nui_rpc")["tempId"].as<uint32_t>() + 1;
            Nui::val::global("nui_rpc").set("tempId", tempId);
            const auto tempIdString = "temp_"s + std::to_string(tempId);
            Nui::val::global("nui_rpc")["frontend"].set(
                tempIdString,
                Nui::bind(
                    [funcInner = Detail::FunctionWrapper<FunctionT>::wrapFunction(std::forward<FunctionT>(func)),
                     tempIdString](Nui::val param) mutable {
                        try
                        {
                            funcInner(param);
                        }
                        catch (std::exception const& exc)
                        {
                            // If you see this, never let an exception bubble up from your rpc function!
                            WebApi::Console::error(
                                "Caught exception leaving rpc function '{}': {}", tempIdString, exc.what());
                        }
                        catch (...)
                        {
                            // If you see this, never let an exception bubble up from your rpc function!
                            // Also, please only throw things that derive from std::exception!
                            WebApi::Console::error("Caught unknown exception leaving rpc function '{}'", tempIdString);
                        }
                        Nui::val::global("nui_rpc")["frontend"].delete_(tempIdString);
                    },
                    std::placeholders::_1));
            return tempIdString;
        }
 
        template <typename FunctionT>
        static void registerFunction(std::string const& name, FunctionT&& func)
        {
            using namespace std::string_literals;
            if (Nui::val::global("nui_rpc").isUndefined())
            {
                WebApi::Console::error("rpc was not setup by backend"s);
                return;
            }
            Nui::val::global("nui_rpc")["frontend"].set(
                name.c_str(),
                Nui::bind(
                    [funcInner = Detail::FunctionWrapper<FunctionT>::wrapFunction(std::forward<FunctionT>(func)),
                     name](Nui::val param) mutable {
                        try
                        {
                            funcInner(param);
                        }
                        catch (std::exception const& exc)
                        {
                            // If you see this, never let an exception bubble up from your rpc function!
                            WebApi::Console::error("Caught exception leaving rpc function '{}': {}", name, exc.what());
                        }
                        catch (...)
                        {
                            // If you see this, never let an exception bubble up from your rpc function!
                            // Also, please only throw things that derive from std::exception!
                            WebApi::Console::error("Caught unknown exception leaving rpc function '{}'", name);
                        }
                    },
                    std::placeholders::_1));
        }
 
        static void unregisterFunction(std::string const& name)
        {
            using namespace std::string_literals;
            if (Nui::val::global("nui_rpc").isUndefined())
            {
                WebApi::Console::error("rpc was not setup by backend"s);
                return;
            }
            Nui::val::global("nui_rpc")["frontend"].delete_(name.c_str());
        }
 
        struct AutoUnregister : public OnDestroy
        {
            AutoUnregister()
                : OnDestroy{[]() {}}
            {}
            explicit AutoUnregister(std::string name)
                : OnDestroy{[name = std::move(name)]() {
                    unregisterFunction(name);
                }}
            {}
            ~AutoUnregister() = default;
 
            AutoUnregister(AutoUnregister const&) = delete;
            AutoUnregister(AutoUnregister&& other) noexcept
                : OnDestroy{std::move(other)}
            {}
            AutoUnregister& operator=(AutoUnregister const&) = delete;
            AutoUnregister& operator=(AutoUnregister&& other) noexcept
            {
                OnDestroy::operator=(std::move(other));
                return *this;
            }
 
            void reset()
            {
                trigger();
            }
        };
 
        template <typename FunctionT>
        static AutoUnregister autoRegisterFunction(std::string const& name, FunctionT&& func)
        {
            registerFunction(name, std::forward<FunctionT>(func));
            return AutoUnregister{name};
        }
    };
}